This was true relatively recently, but I don’t think any WW2 vintage airplanes are still being used for firefighting in the US. After some high profile crashes the Forest Service started limiting the types of aircraft their contractors could use, sometime around 2006 or so IIRC. I believe the oldest currently operating firefighting planes are P2 Neptunes, which were sub hunters built in the late 1940’s, but those are on their way out too.
Part of the problem is that longer and more intense fire seasons have become the norm, which means firefighting aircaft have to fly a lot more sorties, which means a lot more wear and tear on older aircraft and a lot more risk exposure for aircrews.